Rolling Diameter Help

[525iT_Feen]

I used tire calculator and just confused myself further so I figured I'd check here since i'm new to AWD and the stagger even mattering.

18x12 265/35/18
18x10.5 235/40/18

Would that work on a Quattro car?

[Byron]

Yup, those are almost exactly the same OD.

I've heard people say within 3%, but that's over a 3/4" difference which to me seems way too much. Yours are less than 3mm difference though, which is the same as having bald tires on one axle.